Madness Takes Its Toll
by foobar137
Summary: It's time for the annual Skin Horse oversight review of OWCA's use of uplifted animals, which means Perry gets a certain talkative samoyed as a companion for the day. Meanwhile, a sudden breakthrough means there's three mad scientists living on Maple Drive, and Dave and Helen are called in to provide advice. (P&F crossover with Narbonic and Skin Horse.)
1. Prologue

**Trigger warning: bullying**

 **The initial impetus for this crossover was a mental comparison of Isabella's speech to Phineas at the end of "Summer Belongs To You" and Helen's speech to Dave at the end of the "Madness" storyline.**

 **Many, many thanks to Shaenon Garrity for her help with Narbonic canon. Assume any errors in canon are my fault, possibly deliberate as part of the crossover. ("I meant to do that.")**

 **DoctorV is providing art for each chapter; links are in my profile. Thanks to Sabrina06 and DoctorV for beta-reading.**

 **Timeline: (P &F side) Late sophomore year of high school; Phineas, Ferb, and Isabella are all fifteen. (Narbonic/Skin Horse side) Some time after "If I Ran The Zoo" but before "The Terrible, Horrible, No Good, Very Bad Day". Note: this story contains spoilers for Narbonic's main story-line, and for Skin Horse through "If I Ran The Zoo". I've tried to make this understandable for people who have only read one side of the crossover, although it's probably more comprehensible for P&F fans than SH/N fans.**

* * *

Isabella Garcia-Shapiro walked through the grey halls of Danville High School, pretending she couldn't hear the names whispered behind her back. "Freak." "Weirdo." "Psycho." "Crazy."

She sighed. Life had been so much easier when they were younger. Phineas and Ferb had invented cool things, and everyone had loved them. She'd led a strong troop of Fireside Girls that had gathered record numbers of the most obscure patches, largely with Phineas and Ferb's help.

And then, people grew up. They stopped enjoying the things that Phineas and Ferb had made. Some kids literally couldn't see the mutant potatoes running down the street, and everyone else pretended not to. One by one, their friends had drifted away, the stench of unpopularity chasing them off. It wasn't cool to do incredible things any more. The Fireside Girls troop had shed members until, finally, it had just been Isabella and Gretchen. And then Gretchen's mom had pulled her out because of the rumors that Isabella saw things that weren't real.

Phineas didn't seem to get upset about it. Isabella still had a massive crush on the boy, and he still didn't seem to realize it, but he really liked having her around. He was equally a target of derision, and Ferb even more so with his green hair. But the boys kept inventing; they just kept it to themselves, with only her for support. No more city-wide roller coasters; instead, they built invisibility screens and force shields to protect themselves - and her - from bullies. Unfortunately, she'd left her force shield at home today.

Isabella paused at the front door of the school, where a cluster of upperclassmen were gathered on the steps outside, chatting at the end of the day. Several of the cheerleaders were among them, including Karen, one of the leaders of their social circle. Unfortunately, Karen seemed unable to see _anything_ unusual. One of the boys' last public inventions had been a giant robot for the homecoming parade, and when it had been suddenly destroyed, a falling piece had splashed Karen with mud. Karen hadn't noticed the robot or the falling machinery; all she'd seen was Isabella picking herself up, and she had decided that Isabella must have deliberately hit her with the mud. Karen had declared Isabella persona non grata after that, and had done whatever she could to make Isabella's time in school a living hell.

The teleporter in Isabella's pocket felt like it was going to burn a hole right through her jeans, and she could use it as soon as she got outside and away from people, but first…

There was nothing to be done about it. She had to get out, and as quickly as possible. Karen was laughing with her boyfriend, so maybe Isabella could get past without being noticed.

She slipped through the door in a cluster of other students, hoping to make it through the gauntlet unscathed. She was passing behind Karen, thinking she may have made it, when Karen suddenly stuck a foot backwards, tripping her. She tumbled down the stairs, miraculously not bringing anyone else down with her as her books went flying. She picked herself up, finding that she only had some minor scrapes and bruises, and hurriedly gathered her books as the cheerleaders and their boyfriends laughed at her.

She felt something within her _snap_ , and unbidden, an idea for revenge jumped into her mind. She saw how to build it. It was simplicity itself, she just needed to gather the parts. And then she'd show Karen and the rest of her cronies that these things were real. She'd show them all.


	2. Oversight

**Earlier the same day**

Phineas and Ferb's pet platypus, Perry, relaxed on the couch, a blob of teal against the brown of the sofa. He liked quiet mornings like this, although he knew they never stayed quiet for long. Despite his owners' repeated statements that, as a platypus, he didn't do much, this was just a cover for his real identity: Agent P, a top agent for the Organization Without a Cool Acronym. His duty: stop the 'evil' Dr. Doofenshmirtz from taking over the entire Tri-State Area with whatever bizarre invention he'd just created.

His watch beeped and displayed the words, **Report for briefing**. Perry looked around to confirm nobody could see him, then stood up and put on his fedora. The nearest entrance to his secret spy base was through the couch, so he flipped the center cushion and fell through the tube underneath it.

Perry arrived in his lair by transit tube as usual, falling into his chair as spare change and a remote control landed around him. Computers and tools covered the walls, and his chair faced a giant screen.

He was surprised to find the lair wasn't empty. A large white dog - it looked like a samoyed or a similar breed - was sitting next to his chair, wearing a lanyard with what looked like a wallet dangling from it. As he warily eyed the strange dog, the screen came on, showing Major Monogram.

"Good morning, Agent P," he said. "I see you've met Agent Sweetheart. She's an agent from Project Skin Horse, the government agency in charge of, ahem, 'social services for and welfare of non-human sentients'. She'll be accompanying you today on your mission as part of our annual Skin Horse oversight report."

Perry looked at the dog, who said, "Hi!" in a gruff but oddly feminine voice.

Perry blinked.

The dog sighed deeply, and glared at the monitor. "Oh, right. No voice boxes in your uplifted animal agents. That's been noted on your oversight report so many times that they just pre-print it on there now."

Perry gave Major Monogram a suspicious look; Major Monogram looked embarrassed. "Yes, well, we found that if they had voice boxes, it was too likely that they'd accidentally speak where their host family could hear them."

Sweetheart hrmphed. "Right. Host families. I'll need to meet Agent P's 'host family' as well. The..." She pawed through a small notepad on the floor. "...Fletcher-Flynn family."

Major Monogram muttered something about bureaucrats sticking their noses into everything, causing Sweetheart to look sharply at the monitor. "Yes. That's what I do. And I am quite good at it, thank you very much. So, what is today's mission?" she said sweetly.

Major Monogram frowned and looked at a piece of paper. "Doofenshmirtz is probably up to something. Put a stop to it. Monogram out." The monitor winked off.

Sweetheart looked at Perry. "That's _it_? Even Unity gives better briefings than that."

Perry shrugged.

Sweetheart shook her head. "Look, I'm sorry about this. You didn't get any warning on this at all - OWCA didn't decide which agent to assign me to until just this morning. This is just the usual annual oversight that we're required to provide as part of OWCA being able to uplift animals for use as agents. I'll file my usual report that you're all mistreated and it's a miracle you aren't all killed, it'll go upstairs, and it'll be ignored. I've done this a couple times already.

"So, let's go deal with this 'Doofenshorts' person and then I can go meet your host family. Don't worry, I won't talk to them, I just need to see how they interact with you."

Perry gestured to his hovercar.

* * *

Sweetheart looked oddly at the platypus as he politely knocked on the door to the evil scientist's lab. _Okay, the last couple times I did this, they just smashed in through a window._ Off in the distance, she vaguely heard a catchy jingle, but couldn't quite make out the words.

The door opened, and a middle-aged man in a lab coat looked down at them. "Oh, hello, Perry the Platypus," he said. "I see you brought a friend today! Hello, puppy! Won't you both come in?" He patted the platypus on the back as he let them in.

Sweetheart followed Perry in, looking around at the lab. It looked similar to every other mad scientist's lab she'd seen - beakers and flasks, piles of electronics and odd materials, and a few bizarre-looking contraptions hidden under sheets.

The man - presumably, Dr. Doofenwhatever - continued talking. "My apologies for not having an evil plan today, Perry the Platypus and friend. My daughter is graduating from evil college tomorrow, so I'm preparing for her graduation party."

A young woman dressed all in black came in from an adjacent room. "Dad, you don't need to do this. Really."

"Yes, I do, Vanessa. Really. You only get your degree once. Unless you buy another one online, and that's different."

The young woman - Vanessa, apparently - shook her head, then came over and rubbed Sweetheart's head. "Hey, Perry. Who's your friend? Who's a good dog?"

Sweetheart barely kept from rolling her eyes. She sniffed the presented hand, and nuzzled the palm. _Just an ordinary dog here. Nothing special._

"You're welcome to stay for the party if you'd like, Perry. And your friend too," Vanessa said.

Perry shrugged, shook his head 'no', tipped his hat, and led Sweetheart back out the door.

* * *

Phineas Flynn and his stepbrother Ferb Fletcher teleported home quickly after school - there had been a couple too many incidents of kids forgetting about the boys' defense fields and ending up stunned in the hallways, and they did what they could to minimize casualties. Phineas had just gotten his learner's permit, and Ferb was getting one soon, so they were working on a car they could drive.

 _Teleporters are cool and all_ , Phineas thought, _but a really nice car is a work of art in and of itself._

Ferb had found an old battered 1932 Ford Model B - the classic Deuce Coupe - which they were carefully restoring into an old-style hot rod. The boys entered the garage, now largely their domain and workspace. Off to one side was a carefully-organized tool rack; nearby was a small pile of scrap metal they'd created as they removed rusted and damaged pieces. The shell of the car sat on blocks in the center of the garage, its wheels stacked behind it. The engine block sat on the workbench, surrounded by pieces waiting to be attached.

"You know what I miss, Ferb?" Phineas asked, running his hands through his mop of red hair. "Building big. I'd really like to build something really massive again."

Silently, his green-haired brother raised an eyebrow.

"No, we've done enough rollercoasters. I'm thinking of another gigantic haunted house."

Ferb sighed, and spoke in his quiet British accent. "You just want another excuse to hold Isabella's hand."

Phineas looked guilty. "Maybe? If we can't find a way to push her gently over the edge soon, I'm afraid she'll snap on her own. Karen and her crowd are really starting to push her hard, and if Isabella goes mad, she could take out half the town."

"We could just try to track down the madness cure."

"I told you before, Ferb. If she takes it, I'm taking it."

Ferb shook his head.

"You saw what it did to Baljeet when his parents gave it to him," Phineas said. "He went totally reality-blind."

"I know," Ferb said quietly. "But the longer we wait, the more damage Isabella might do."

"She's worth the risk," Phineas said.

* * *

Perry led Sweetheart into the garage, hoping that the boys were being relatively normal and just working on the car. Fortunately, his hopes seemed to be granted.

"Oh, there you are, Perry," Phineas said. "Who's your friend?" He held out his hand non-threateningly, so that if she wished, she could sniff him. She did, and licked his hand in welcome. Perry hoped the boys didn't notice her wince at the taste of the grease on his hand.

Phineas scritched the dog between the ears, causing her to relax, as he looked at her neck. "No collar. That's odd. There's this…lanyard instead." His eyes narrowed. "Where are you from?"

Before he could continue with this line of thought, he was interrupted by Isabella running into the garage. Pinky chased after her, barking at her heels. "Hi, Isabella!" he said, but she didn't respond, instead heading directly for the tools.


	3. Madness

_I'll show them. Oh, how I'll show them all_ , Isabella thought. Ideas bounced around her brain, caroming off each other and colliding into newer, bigger ideas as the madness overtook her.

She needed more resources. She could disassemble her teleporter, but that wouldn't give her enough to build the devices she imagined. She had more things at home. She needed to go and get them. She pulled her teleporter out of her pocket, a small white ovoid with a button on one side. She looked at it, resting in her palm, and could see now how it worked. It all made so much sense now. _Zero-point generator there, power cycles through there, warp generator to create the inter-dimensional portal, miniature centrifugal compensator to absorb rotational velocity, neural interpretation matrix…_ She shook her head before she could be seduced by the beauty of the teleporter's design, and pushed the button on the side. It picked up her desired destination from her thoughts, and took her home in a flash.

She burst through the front door of her house. Her mother said, "You're home fast. Are you okay?"

Her brain seemed to have gained fantastic new abilities. A small portion of her brain remembered how to act like the old Isabella, a replica of what she used to be. Meanwhile, the rest of her thoughts could continue to plan her revenge.

"I'm fine, Mom. Just picking up a couple things." She ran up the stairs and found the translucent wafer of her invisibility screen and the brassy sphere of her force shield, sitting on her dresser. Her pet chihuahua Pinky looked up at her and barked.

 _Invisibility screen, power source, wave-bending field generator, optical enhancement… Force shield, power source, energy sensor, dissipation matrix, field projector…_

 _Not enough. I need more resources. I could make a decent death ray with these, but that's about it._

 _Phineas and Ferb have everything I need._

She looked at herself in the mirror, and she recognized the look of madness in her eyes, like one she'd seen in Phineas and Ferb's eyes. A sudden realization dawned on her, pausing even her madness-driven intellect. _Phineas knew. That was why he wouldn't go out with me. He's mad too. He knew all along. Ferb too._

She'd get her revenge on them as well, for keeping her in the dark so long. They must have been jealous of her. They knew she'd be smarter than them once she went mad. They would pay for that. She'd make them grovel before her. Phineas especially; maybe once he was done groveling, she could find a more interesting use for him. But first, she needed to raid their supplies. She needed revenge on Karen, even more than Phineas.

She raced back down the stairs, Pinky following right behind. Her mental replica shouted, "I'm going across the street, Mom," as she crashed back out the front door. Her mother said something in response; she didn't hear what.

Phineas and Ferb were in the garage, next to the car they'd been working on. Perry sat near them, and Phineas was greeting a large white dog she didn't recognize. "Hi, Isabella!" Phineas said.

She'd stopped the part of her brain pretending to be the old Isabella on the way across the street, and her brain was working full-time on her plans. She could see it in her head: a mechanical suit, twenty feet tall, like the Beak suit but bigger, and only meant for one person. Looking like a giant version of herself. But much more heavily armed. A laser on each arm, and missiles on the shoulder. If she hurried, she could build it and fly it to school before cheerleading practice finished. _They'll rue the day_ , she thought.

"Isabella?" Phineas asked. "Are you okay?"

She headed straight for the tool rack, grabbing his flange tuner in her left hand and a crescent wrench in her right.

Ferb said, "It's happened. Code Magenta. Execute G-2."

Phineas tapped Isabella on the shoulder. She turned toward him, and he took her face in his hands and gave her a deep kiss.

She could feel her focus slipping. She dropped the flange tuner, and barely hung on to the crescent wrench. This was what she'd wanted, craved, needed...but she had to get her revenge first. And he still needed to grovel. She broke off the kiss, and said, "Hold that thought, Phineas," as she turned toward the pile of scrap metal.

Phineas sighed and said, "You were right, Ferb," as Isabella felt a pinch at her neck. And then everything went black.

* * *

Sweetheart boggled. The girl had clearly just had her first madness breakthrough. And these boys had not only expected it, but worked out plans on how to handle it. After the kiss had failed to calm her, the green-haired one had pinched her shoulder and knocked her out with hardly any effort. The red-haired boy - Phineas - had caught her as she fell, and was cradling her head in his lap as he sat on the floor of the garage. The chihuahua who'd followed her sniffed at her, then looked up at Phineas expectantly.

"It's okay, Pinky," the boy said. "She just went mad. You knew it was coming eventually."

"What are you?" Sweetheart asked, causing the boys to jump. Perry chattered and glared at her, and Pinky suddenly looked at her, his eyes narrowing.

"That depends," Phineas said calmly. "Who's asking?"

"Federal agent." Sweetheart tried to make it sound impressive, but being in a tool-filled garage with what appeared to be three mad scientists was moderately terrifying, and the fact that one of them was unconscious didn't actually help matters.

Phineas's eyebrows went up. "What agency?"

Sweetheart sighed. "Project Skin Horse."

The green-haired boy - Ferb - spoke up. "Non-human sentient social services. You're here to monitor Perry, then?" he asked in a deep British accent.

Perry chattered, alarmed.

Phineas smiled thinly. "It's okay, Perry. She's already seen that there's madness in the house - if she decides to hang us out to dry, the OWCA will pull you out of here anyway."

Perry sighed and pulled his fedora out from behind his back. Putting it on, he said, in a thick Australian accent, "I s'pose yer roight."

Sweetheart blinked. "...what?"

"We gave him a voice box a couple years ago when we realized his secret. Please don't tell his bosses, we'd hate to lose him," Phineas said. "And Isabella'd be devastated to lose Pinky, although he's going to need to report in that she went mad, I assume."

Pinky pulled out a fedora of his own, stood, and nodded his head sadly.

Sweetheart shook her head. "Wait just a minute here. What _are_ you people?"

Phineas laughed. "That's a good question, actually. We're mad scientists. Just not evil ones. As near as we can tell, we broke through at about five years old - far too young for the initial 'Show Them All!' response, so we never turned evil the way most do. And since we had each other for support, we didn't fall into evil madness from there. At least, that's the best explanation we've been able to come up with so far." Phineas stroked Isabella's hair and smiled softly. "We've been waiting for her to break through for years. I was hoping we could get her through it more gently, but...hopefully there was no permanent damage. I'm just glad we caught her before she could hurt anyone else. Maybe…maybe there's hope."

Sweetheart boggled at the boy. "You broke through at _five_?"

"About there. It wasn't really a quick, sudden break - it probably took a week or two, so it's harder to pin down just when it happened. We started taking notes about it at six."

"Can I call someone? A friend of a friend studies mad scientist breakthroughs - she might be able to help," Sweetheart offered.

"Sure. Just...make sure they can be trusted, okay? We don't want to lose Perry or Pinky."

"We're talking about mad scientists. 'Trusted' is a relative term," Sweetheart said.

* * *

Artie put down the paper he was grading as his phone rang. Looking at the caller ID, he frowned and answered the phone. "Sweetheart? What's up?"

"Artie, I need a favor from you. Didn't you say your creator did some work on unusual mad scientist breakthroughs?"

"Yes, she did. As both researcher and subject, actually."

"I have a couple kids here who say they broke through around age five. And they're not evil. They need some advice dealing with a friend who just broke through. Think she'd be interested?"

"Five? Two five-year-olds with simultaneous breakthroughs?"

"They say they have notes back to age six."

"I think she'd be interested, yes. Want me to check?"

"Please do."

* * *

Sweetheart put a paw up and pulled the headset off her ears. "Artie says they'll be teleporting over in a few minutes."

"Who's 'they'?" Phineas asked, still sitting on the floor with Isabella.

"His creator and her husband. She wants to talk to you about breaking through so young - that's the carrot to get her here - and he'll talk to Isabella about coping with people who've been mad longer than you."

Ferb stood up and said, "If they're teleporting, I should probably go turn off the teleport redirector."

Brief klaxons went off from both boys' phones.

Ferb took a deep breath and headed toward the basement. "Or let them out of the holding cell."

* * *

 **There's two - two - TWO! pieces of art for this chapter, linked from my profile.**


	4. Help

Dave looked around the small cell in the basement. "I get it!" he said. "Teleportation anywhere in the field area gets dumped into this cell, and attempts to teleport out of the cell fail. I think we need to set this up on the island."

Helen glared at him. "What, so the Daves don't drop in unannounced?"

Dave ignored her comment. "I wonder how much energy it takes?"

"About three hundred watts to cover the house," a British voice said from the basement door. Dave looked up at the tall young man with green hair who had evidently spoken. "My apologies; I didn't find out you were arriving in time to turn off the redirector."

"Understood," Dave said. Helen continued to seethe.

Across the room, the green-haired boy pulled a lever which released the cell door. As Dave and Helen stepped out, he greeted them with hand outstretched. "Thank you for coming to help. I'm Ferb Fletcher."

Dave shook the boy's hand. "Dave Davenport."

Helen glowered and took the boy's hand as well. "Helen Narbon."

Ferb's eyes went wide, and he bowed low over her hand. "I'm honored. We've both read both your mother's report, and the Tinasky final report, hoping for something we could use to help Isabella - that's the girl who just went mad today. We kept notes on her case, in case they were useful to someone. In addition, we've notes on our own cases, from the point we realized we were mad, at about age six."

Helen's frown went away. "Wait, you have notes from age _six_? And on another pre-madness case? Can I have copies?"

"If Isabella says it's okay you can have hers, and I'll gladly give you the notes we kept on ourselves. Come on, let's bring you up to the garage so you can see what we're working with."

They followed the boy upstairs and through a normal-looking suburban house. Inside the garage, a wiry red-haired boy was cradling the head of an unconscious girl with long black hair. A platypus and two dogs, a chihuahua and a large white samoyed, sat on the floor near him, all in a conversation together.

The red-haired boy extended a hand up. "Hi, I'm Phineas Flynn, and this is Isabella Garcia-Shapiro. Sorry we can't get up to greet you."

"Dave Davenport." He shook; the boy's handshake was solid.

"Helen Narbon." Helen shook his hand as well.

Phineas's eyes widened. " _The_ Helen Narbon?"

"Technically, _a_ Helen Narbon," she said, grimacing.

"Oh, right, cloning. Sorry. Still...one of the foremost authorities on the causes of madness and dealing with the pre-mad." He looked over at the white dog. "Thank you so much, Sweetheart. We owe you for this."

The large white dog smiled and wagged her tail. "Thank you." She put up a paw. "I'm Sweetheart, from Project Skin Horse. Artie's friend."

Dave and Helen shook appropriately, and the platypus - who was wearing a fedora and standing on his hind legs - put up a hand and said in a thick Australian accent, "Perry the Platypus, with O.W.C.A." Pointing at the fedora-clad chihuahua next to himself, he said, "Pinky the Chihuahua, also with O.W.C.A."

As he shook the platypus's hand, Dave pondered. "I don't know the local mad scientists here. Who's your nemesis?"

"Heinz Doofenshmirtz."

Dave nodded. "Right. Weird devices with an idiosyncratic naming scheme. -inators?"

"That's the bloke," Perry confirmed.

"I think I met him at the North American Mad Science Symposium last year. He was ranting about his latest experiment being ruined by a..." Dave paused, and looked at Perry. "...platypus. Well, then. And here I thought he was just being metaphorical."

"Told you," Helen said.

"And you?" he asked the chihuahua, shaking his paw.

"He doesn't have a voice box yet," Perry said. "His nemesis is Esmeralda Poofenplotz. She's a bit more bush-league, you probably haven't heard of her."

Dave shook his head and looked at Phineas. "You sure this is what you want? If you want to start running, we can try to hold our newly-minted madgirl back and give you a head start."

Phineas chuckled, his hand on Isabella's forehead. "I'm sure."

Helen lightly punched Dave in the arm, then looked at Phineas. "She might not be the same as she was. She might not want you anymore. You might not want her anymore."

"Yeah, like I'm so unlikely to be interested in a super-genius version of a girl who was already gorgeous, clever, determined, and creative."

Dave laughed, and shared a secretive smile with Helen. He said, "So what did you do to knock her out, and when should it wear off?"

Ferb spoke up. "Vulcan nerve pinch. She should wake up presently."

Isabella's eyes fluttered as if in response to his comment, and then snapped open, looking at Phineas. "You!" she said.

"Yes, me," the boy responded. "Feeling better?"

"I...I don't know," she said, sitting up slowly and looking around. "Things make more sense now. It's like my brain was foggy forever, and now the fog is gone. Who are these people?"

Phineas pointed. "Sweetheart, agent of Skin Horse. Perry and Pinky you already know. Dave Davenport and Helen Narbon, mad scientists."

Dave waved.

Isabella turned toward Phineas, her eyes narrowing. "You knew all along, didn't you? Why didn't you tell me?"

Phineas looked down at his lap. "You wouldn't have believed me? I was still hoping we could find a gentle way to get you through?" He looked back up, hesitantly meeting her eyes. "I didn't want to hurt you."

She stood up angrily. "Nice job," she said bitterly. Phineas closed his eyes and winced.

Dave cleared his throat and said, "Isabella? Can we talk for a minute?"

* * *

"Vanessa, I've figured out what I want to give you as your graduation present. Since my baby girl is graduating from evil college," Heinz said.

Vanessa looked up at her father from her seat on the couch. "It's not evil college, Dad. It's just college."

"You weren't the one receiving the tuition bills. Trust me, it's evil."

"Neither were you, Dad. Mom paid for it."

"Yes, but she complained about how much it cost to me. Usually while saying it'd be easier to pay for it if she didn't have to pay my alimony. Aaaanyway, I figured that what I'd give you as a present is...the Entire Tri-State Area!"

Vanessa rolled her eyes. "You'd have to take it over first, Dad."

"Yes, but you see, normally I'd be stopped by Perry the Platypus. But today, he's already gone home, so he won't be stopping me. When he was here, I planted a tracker on him and attached it to the targeter for my energy-drain-inator. So when it fires, it will drain all the energy from Perry the Platypus and anyone with him, so he won't be able to stop me."

He pressed a button on the energy-drain-inator, and a bright orange beam fired out into the distance.

* * *

"So...Dave? What did you need to talk to me about?" Isabella asked, standing in the front yard with the man. He was short, with scraggly brown hair and glasses, dressed in a lab coat that was mostly white except for a few grease stains. He seemed nonthreatening, until you looked at his hazel eyes, which had a hint of being...off. She recognized it as that faint look of madness that she'd seen in her own eyes earlier.

"I've been where you are," he said. "Suddenly discovering that the person you've been interested in is mad, and knew all along that you were at risk of going mad. You're wondering why he didn't send you away, why he didn't try to drive you around the bend, how he could possibly have cared about you when you were as dull as...well, a normal person, whether he was using you as just another experiment."

She stopped and stared at him. "Yes. How…?"

He nodded his head toward the garage. "Been there. Done that. We worked it out, eventually."

"That was Helen?"

He nodded. "Yes. We'll have to get you a copy of the Tinasky study."

"What's the Tinasky study?"

"It was the report Helen wrote up on me before I went mad. She studied me for years. I was her lab monkey, her henchman, her experiment...and more. And she tried to save me, and sent me away to live among the normal people."

"Did it work?"

"No. I went to work for another mad scientist, and finally went mad myself. I almost blew up the whole world, but Helen risked it all to save me."

Isabella pondered this briefly, then stared back at the garage, as if by looking hard enough, she could see into Phineas's head. Ferb and the large white dog were wandering out of the garage, talking to each other.

"So, what now?" Isabella asked. "I go in there and say, thanks for letting me go mad, let's make out?"

"What's next is up to you. What do you want? Do you want him? Do you want to never see him again? Do you want to go back to normal?"

"That's an option?"

"Helen has a cure. She's got most of the side effects out now."

Isabella looked at Dave. "No. I can't go back to what I was. And...I can't just walk away from him. But how could you forgive her?"

"Ask yourself this - if the situation were reversed, what would you do differently?"

Isabella closed her eyes and thought. "...I...don't know." Her shoulders sagged. "I don't see a better solution." She saw Ferb nearby, chatting with the white dog, and called him over. "Ferb? Dave says there's a cure for madness. Did you and Phineas know about it?"

"We did," Ferb said. "I suggested using it on you, but Phineas refused. He said that he didn't want to be mad without you, and if I gave you the cure, he was taking it too."

"He'd give up inventing...for me?"

Ferb nodded slowly.

An orange beam came down from the sky, striking the garage; Ferb's shield fired up, preventing the four of them from being hit.

"What was that?" Sweetheart asked.

Looking inside the garage, Isabella saw that everyone inside seemed to be out cold.

"Looks like some sort of...sleep ray? Energy drain ray?" Dave said. "What's this shield that protected us, and can I get one?"

"Force shield that Phineas designed," Ferb said. "Isabella should have one as well. Phineas must have turned his off when we got home."

Isabella pulled hers out of her pocket, along with her teleporter and her invisibility screen. "Sorry, they were turned off."

"Where could the beam have come from?" Isabella asked, mentally trying to reverse the path of the beam and figure out its origin.

"My money's on Agent P's nemesis," Sweetheart said. "He seemed to be in a rush to get us out of there today."

"That…would make sense," Ferb said, nodding slowly. "Shall we head over to visit Dr. Doofenshmirtz, then?"

"Let's," Dave said.

* * *

Vanessa looked up from the magazine she was flipping through, the New Journal of Malology, at the clock on the wall. "So, Perry should be coming through the door…right…about…now."

Heinz winced, then looked up at the door, which remained resolutely unopened. "He's not there."

"That's weird," Vanessa said. "Do you think it actually worked?"

"Let me check," Heinz said, turning on a small screen on the side of the targeter for the energy-drain-inator. "Ooh, the tracking device reports 'target neutralized!' I might have actually hit Perry with it!"

"Huh. You actually got something to work right. So now what? How are you going to take over the…" Vanessa paused, then did her best imitation of her father's voice, "Entire Tri-State Area?"

"I hadn't really thought that far ahead," Heinz said reluctantly.

Vanessa put her face in her hands. "Oh, Dad…"

"I know! I'll build a Duplicate-inator that will make a bunch of robot duplicates of myself…"

"Been done," Vanessa said, pointing at her magazine. "Professor Madblood tried it, they all turned on him when somebody shapeshifted to look like him."

"Oh, right. That was where I got the idea from. But what are the odds somebody'd be able to do that, though?"

"Around here? About 95%, I'd say."

Heinz sighed. "I suppose." A thought occurred to him, and he smiled. "But if I'm trying to give the Tri-State Area to you, then I make them all loyal to you instead of me! And then duplicating me doesn't get them anywhere!"

Vanessa rolled her eyes and went back to her magazine. "Sure, Dad, you do that."

* * *

 **There's another image linked in my profile, but apparently the links aren't working right at the moment; I'm still investigating.**


	5. Confrontation

Dave looked up at the large, oddly-shaped building. "This is it?"

Ferb nodded. "Doofenshmirtz Evil, Incorporated. It's up in the penthouse, from what Perry's told me."

"Yeah, that's where we were this morning," Sweetheart said. "It was really weird. He just knocked on the door, and the mad scientist let him in."

"Perry's pretty good friends with his nemesis, actually," Ferb said. "He doesn't attempt as much actual evil these days. It must be a special occasion of some sort."

"His daughter was graduating from college," Sweetheart said. "Evil college, he claimed."

"Vanessa," Ferb said quietly, savoring the name, and Dave raised an eyebrow at him.

"So, he's going to try to take over the world as a graduation present?" Dave asked.

"Not the whole world. Just the Tri-State Area. He's never had very big dreams," Ferb said.

"Okay. So, let's go in there, take him out, and destroy whatever device is draining Phineas," Isabella said decisively.

"And Perry, and Pinky, and Helen," Ferb added.

"Yeah. Them too."

Shaking his head, Dave followed the two teenagers and the dog into the building.

The elevator ride to the top was interminable, with everyone quietly pondering what they'd find. Dave thought through what he remembered of Doofenshmirtz - he was an older man, who would be tall were it not for his perpetual slouch. He built devices that, even by the standards of mad science, were bizarre and unworkable. He'd rambled on about being thwarted by a platypus, which didn't say much about his skills in a fight.

Not that Dave was exactly an expert at it either.

"Um," he said, "if he doesn't just surrender when we show up, does anyone here know how to fight?"

"I know several martial arts," Isabella said.

"I'm not bad in a scrap," Ferb said.

"I was created to take over the entire US," Sweetheart said.

"Huh. Okay, then," Dave said.

The elevator dinged as the doors opened onto the top floor. An empty hallway stretched out ahead of them, with one door in the center of one wall. Another door to one side was marked 'Stairs'.

"This way," Sweetheart said, leading them to the door. "Um, Perry just knocked and we were let in."

Ferb shrugged and knocked on the door.

"You're too late, Perry the Platy…oh," Heinz said, opening the door and then stopping short at the group of people waiting for him. "Hello, puppy, it's nice to see you again, but where is your friend Perry the Platypus? I was expecting it to be him knocking at the door. And who are your new friends?"

"Stuff it, Doofenshmirtz," Isabella said, pushing past him and looking around. Dave glanced in through the open door. The penthouse area was filled with furniture and old electronics, with a large, boxy machine in the corner flashing lights while a giant ray-gun-shaped device on the balcony pointed downwards. She turned to Heinz and asked, "Did you knock out my boyfriend?"

"I don't _think_ so…" Doofenshmirtz said, looking at her, confused. "I mean, I was trying to use the energy-drain-inator on Perry the Platypus, and maybe somebody got caught in the crossfire?"

"Dad, you're going to just give it all up again, aren't you?" a young woman, dressed all in black with long brown hair, said from her seat on the couch. "Because that's what you do. One setback, and you just surrender."

"Well, even though I may have taken out Perry, they sent _three_ mad scientists after me. I mean, how can I beat three mad scientists? And a dog. Hello puppy!" Heinz knelt down to scritch Sweetheart's head.

Sweetheart's eyes closed. "Oh, that feels good," she said.

"Wait, what? You're…Agent D?" Heinz said, standing up quickly. "But you can talk, that's unusual."

"Why would I be Agent D?" Sweetheart asked.

"Well, I'm just assuming. D for dog, you know."

"No, I'm not with OWCA. I'm with Skin Horse."

Heinz furrowed his brow. "Wait, what?"

Sweetheart rolled her eyes. "I was auditing Agent P today, before I got dragged into this…mess. But right now, I'm partly responsible for his wellbeing, so…I need you to stop draining his energy."

"I think I've got it," Isabella said, looking at the ray-gun on the balcony. "Self-destruct button is right here." She pointed at a large red button on the side.

"Seriously?" Dave asked, shaking his head. "No wonder the platypus always wins."

"It's traditional," Heinz said defensively. "Hey, didn't I meet you at the North American Mad Science Symposium?"

Dave nodded. "Yeah. Sorry, I didn't realize you were talking about a literal platypus."

With a _ding_ , a panel slid up on the machine in the corner, and an apparent exact duplicate of Heinz stepped out. Another _ding_ followed about thirty seconds later, and another duplicate joined the first.

Dave rolled his eyes. "Oh, God. Not Madblood again."

"No, no, I'm being more clever than that," Heinz said.

Another _ding_ signaled a third duplicate stepping next to the first two.

"Um, isn't anybody going to stop that thing?" Sweetheart asked.

"Oh, right," Isabella said, smacking the red button. The device exploded, knocking her back a bit and covering her front with a fine layer of soot, which she wiped off, laughing.

"Not that one," Sweetheart said. "The duplicate generator." Another _ding_ echoed around the room.

* * *

Vanessa watched Isabella hit the self-destruct button, laughing as her father's hard work was yet again destroyed. This time, it wasn't even Perry doing it, it was just Isabella - just a kid.

Something in Vanessa's head _clicked._ They were laughing at him. Again. And laughing at her, for putting up with him.

She'd been embarrassed about her father, and then defensive about him, and even proud of him on occasion. And now...now, once again, they laughed at him.

No more.

It was so obvious. The robots would fight for her. Every tool she'd need was here.

Dad's ambition was too small. He tried to take over the Tri-State Area because he couldn't grasp the concept of taking over the world.

She could see it. She could see it all.

Another _ding_ sounded as a fifth robot joined her army. It was a start. She'd need to accelerate production, and defend the generator. And with these robots, her father would indeed give her the world.

The fools. They'd rue the day.

She laughed a deep, evil laugh and turned to her father's tool chest.

* * *

Ferb's head snapped up as he heard Vanessa's laugh, while Dave muttered something obscene.

"Two breakthroughs in one day," Ferb said drily. "Must be something in the water here."

"We need to stop her before she kills us all," Dave said.

"Wait, what just happened?" Sweetheart said.

"Vanessa just went mad," Ferb said.

"You fools!" Vanessa cried. "Robots, grab them!"

"Sure thing, pumpkin!" the five - now six - robots said in unison. Ferb leapt back, but the robots were faster, and one of them quickly grabbed his arm. He reached into his pocket with his free hand, grabbing his deactivated defense shield, but the robot said, "Ah-ah-ah, no fair," and plucked it out of his hand before he could turn it on.

Ferb paused a bit, feeling the robot's implacable metallic grip, and looked around to see how everyone else was faring. Isabella had pulled out her invisibility screen, and vanished as a pair of robots converged on her. Sweetheart leapt forward, tackling one of the robots, which fizzled out and went limp underneath her. The fifth robot was closing in on Dave, who vanished with the _ka-zap_ of a teleport remote.

Ferb's eyes narrowed, and he slipped his hand into his pocket again, bringing out his teleporter. The robot dropped the defense shield and reached for the teleporter, and Ferb envisioned the air outside the window as the robot tapped the button in the process of grabbing the device.

With another _ka-zap_ , the robot vanished, only to appear in mid-air on the far side of the glass. Ferb saw a very surprised look on its face in the instant before it plummeted out of sight.

Ferb picked up his defense shield and activated it just as the robot that had been chasing Dave approached him. It reached out, then was thrown backwards as it hit the shield. It sparked as it hit the floor, and didn't move again.

The sixth robot had been joined by a seventh, and the two of them had joined forces to grab Sweetheart. The dog stretched her neck, trying to bite them, but they carefully kept out of her reach.

The robot that had been approaching Isabella was carefully looking around the ruins of the self-destructed -inator. Suddenly, its legs were swept out from under it, and its head was smashed into the floor by an invisible force.

"Vanessa!" Ferb called out as. "You're better than this! Don't let the madness control you!"

She laughed bitterly. "Too late, Ferb. You're all too late." She opened a panel on the machine that was creating robots, and started to work inside it. The machine suddenly sped up, new robots coming out mere seconds apart. The newer robots seemed to move faster as well, and a pair of them were quickly flanking Ferb. He lunged toward one, hoping that his shield would disable it, but the _crackle_ of the shield seemed to dissipate around the edges of the robot. It reached for him, and he quickly backed off, right into the other robot. It locked its hands around his arms, holding him in place helplessly.

Isabella's invisibility screen suddenly switched off as she integrated it into the ray gun she was building. With a lethal smile, she pointed it at the nearest robot, heading toward her, and a bolt of light blasted the robot in the chest, knocking it to the floor in a heap.

"Blast the machine, Isabella!" Ferb called out, and Isabella pointed her ray gun at the giant box that Vanessa was working on. The beam struck the box, and a barely-visible glow along the edge of it sparkled as its shield absorbed the attack.

"Drat!" Isabella shouted as she changed her aim to the robots. Two more fell quickly to her shots, but then two more leapt in from the sides, disarming her and restraining her arms. Her ray gun clattered to the floor.

"Now I have you all," Vanessa said with an evil grin.

Vanessa's father stuck his head out from under a table. "Oh, good, sweetie! Nicely done! Now we can take over the..." He took a breath, but Vanessa interrupted him.

"No, Dad. No. I'm not taking over the Tri-State Area."

He looked up at her, surprised. "You're not?"

"No, Dad. I'm taking over the _world._ "

With a _ka-zap_ , Perry appeared on the balcony, holding Dave's teleport remote. The robots converged on him, but he dodged and evaded effortlessly, pausing only to throw one of them into the entrance of the machine just as another was trying to exit. The collision pushed both of them back into the bowels of the machine, which began to make loud beeping noises as its sides bulged threateningly.

Vanessa's father ducked back under his table while Vanessa shouted, "No!" As if in slow-motion, the machine exploded, throwing her back against the wall.

She pulled herself back up, thrusting a finger at Perry. "Robots! _Destroy him!_ "

Ferb felt the metallic hands restraining him loosen as the twenty or so remaining robots moved in unison toward Perry. He looked at Isabella quickly, and saw her surreptitiously moving toward her ray gun, lying on the floor nearby. He signaled to her, palm down, indicating that she should stay quiet for the moment. Sweetheart, meanwhile, was stalking along behind the robots, evidently trying to get near Vanessa.

Perry was being backed into a corner by the robots. He had dropped to a combat stance, but the robots weren't giving him an opening to take them out individually.

"Excuse me! Coming through!" Vanessa's father said, rushing through the robots who all looked like him. He got in front of Perry and put his arms out to shield him. "This is _my_ nemesis," he said, "and I can't let you hurt him. That's _my_ job."

"Dad, get out of the way or they'll _kill you_ ," Vanessa said angrily.

"Robots! You are my creation! I command you to stop!"

The robots continued towards him silently. "You gave me control of them, remember?" Vanessa said.

"Oh, right."

Ferb crept along the wall toward the corner where Vanessa was gleefully watching Perry's impending doom. Sweetheart was waiting there, and pointed with her nose. "Force field," she said quietly, and Ferb saw the faint flicker in the air.

Ferb nodded, and pulled out his defense shield. "Wish me luck," he said, turning it on and stepping forward. The force fields crackled as they touched, and then with a spark from a field-generator behind Vanessa, both went down.

Ferb and Sweetheart rushed forward as Vanessa turned toward them. "What? Robots!" she called out as Sweetheart leapt at her, knocking her down. Sweetheart stood on Vanessa's chest, growling and practically daring her to move.

"Call them off," Ferb said. "Tell them to stand down." The robots, awaiting new orders, had turned toward the trio, staring silently.

"No! You cannot stop me! I…" Vanessa went silent as Ferb gave her a nerve pinch, knocking her unconscious.

"Isabella? Burn 'em down," Sweetheart said, stepping off of Vanessa.

"With pleasure," Isabella said, turning her ray gun on the unmoving robots and blasting all of them.

Perry's hovercar popped up next to the balcony, carrying Dave, Helen, Pinky, and Phineas. "Aw, you didn't leave any for us?" Phineas asked with an impish smile. Isabella glared at him, briefly pointing the ray gun in his general direction before sticking it in her belt.

* * *

 **Art for this chapter, again, is linked in my profile, but that doesn't seem to work right now. It's all in my tumblr at foobar137 dot tumblr dot com.**


	6. Aftermath

Phineas leapt over the side of the hovercar, landing on the balcony. Off to one side, Vanessa's father was making sure that Perry was unhurt. Ferb was kneeling next to the unconscious Vanessa, while Isabella sat nearby, pointedly not looking at Phineas. Sweetheart trotted away from them, toward the balcony.

"About time you showed up," Sweetheart said, falling into step next to Phineas.

"Sorry. Dave teleported in and helped us all wake up, and then gave his teleport remote to Perry, to get him here faster."

"That was all that saved us, actually. Without Perry, we'd all be doomed."

Behind him, Pinky hopped out of the hovercar and headed over to Isabella. She sat down and pulled the chihuahua into her lap, stroking him gently as she stared off into space. Phineas sighed and looked back down at Sweetheart.

"There's no way we can keep OWCA from finding out about this, I suppose," he said.

"No, I have to report it all, unfortunately."

He took a deep breath and nodded sadly. "I figured." He looked over at Perry wistfully; the platypus was rolling his eyes and pushing the mad scientist back. "It's not like he gets any say in it. He doesn't really have any rights as far as OWCA is concerned."

Sweetheart stopped in her tracks, and a devious smile crept across her muzzle. "Let me see what I can do," she said, and trotted off toward the telephone.

Phineas watched her go, then went to sit by Isabella. She glared up at him silently, still stroking Pinky.

"I'm sorry I didn't tell you," he said.

"I know," she said. "I understand. I'm just…" She paused, looking away from him for a moment. "What do we do now?"

Phineas extended his hand. "Hi. I'm Phineas. I live across the street from you. It's nice to meet the real you, finally."

Isabella laughed, and shook his hand. "I'm Isabella. Nice to meet the real you, too." She looked around. "So do I need to build something like this now?"

"You can do whatever you want. What sounds good?"

"Taking that car you and Ferb are working on and turning it into a giant mecha that I can stomp cheerleading practice with."

Phineas chuckled. "Tempting. If you're planning to go on to football practice afterwards, I might be willing to help. But it's probably not a good idea. Ferb likes the car too much. Hey, can I take a look at that ray gun?"

She handed it over; he recognized most of the parts, as it was mostly made of the defense shield and invisibility screen he and Ferb had given her. "Oh, nice. You turned the optical enhancement into the focusing element. That's really clever."

She smiled briefly, and then her expression became serious. "Ferb said you threatened to take the cure if he gave it to me."

"Yes."

"Why?"

He looked away for a moment. "Because I knew that once the real you came out, she'd be incredible." He clasped her hand, squeezing it briefly. "I understand that you need some time to figure things out. I'm here to talk, whenever you want. No obligations."

"Thanks. Right now…I think I just need to think for a bit."

He nodded and stood up. He nodded to Ferb, who was watching over the unconscious Vanessa. She was starting to twitch like she'd be waking up soon. Ferb nodded back, then raised an eyebrow toward Isabella. Phineas gave him a thumbs-up before walking over to where Perry was talking to Vanessa's father.

"Heinz, I'm foine. She'll be roight," Perry was saying.

"Yeah, they'll keep sending him to deal with you," Phineas said. "It's us they'll take him away from."

"I'm just worried they'll reassign him to Vanessa now," Heinz said. "I know it's silly, but I…I don't want to have to share my nemesis."

"Actually, I think you'll both be fine," Sweetheart said, trotting up behind Phineas. "I just talked to my boss, and she thinks we can make OWCA bend a bit. For both Perry and Pinky."

"That'd be great, Sweetheart," Phineas said. "How?"

"Wait, wait. Your name is Sweetheart? Seriously?" Heinz said. "Because…" He trailed off as Sweetheart's ears flattened and her eyes bored holes in him. "You know, never mind."

With a quiet, "Hmf," Sweetheart turned back to Phineas. "The rules about keeping the family safe don't apply to mad scientists. There are a few cases of nemeses moving in together, you see, to simplify people's commutes. So as long as everybody who knows about Perry and Pinky is mad, then you're fine."

"Ace!" Perry said.

"Yeah, well, least I could do after getting you into this mess in the first place," Sweetheart said.

"No worries, mate. Good dog." Perry reached up and patted Sweetheart on the head; she practically glowed.

"Thanks, Sweetheart," Phineas said. He walked back toward the hovercar, where Dave and Helen were quietly talking. They glanced at each other as he approached, and Helen nodded as she headed over to talk to Isabella.

"I was serious about running, just so you know," Dave said. "You can still get a decent head-start."

"I know." Phineas looked over to where Helen was taking a seat by Isabella. "I don't think I want to."

"I can promise you one thing, then. Your life won't be boring."

Phineas looked around the room. Vanessa had apparently awoken and sat up, and was talking quietly to Ferb. He said something, and she laughed. She shook her head, and then brushed her hair back from her eyes as she looked at Ferb.

Isabella was talking to Helen, who was holding Isabella's ray gun, while Isabella was holding a blobby weapon of some sort as Pinky looked over her shoulder.

Heinz and Perry had helped each other up, and were walking toward Vanessa as Sweetheart went toward Isabella and Helen. Phineas turned to Dave. "You know, I've spent my whole life making sure it wasn't boring. I don't think I'll object if I got what I wanted."

* * *

Many, many thanks to DoctorV for providing art. Links, again, are in my profile.


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